Layer-by-layer self-assembly: The contribution of hydrophobic interactions

The layer-by-layer (LBL) adsorption of polyelectrolytes and other compounds is considered to be the result of electrostatic attraction between ionic side-groups of a polymer backbone to oppositely charged groups located on the surface of a substrate. The energy of electrostatic attraction, transformation of ionic atmosphere and the hydration shell around a polyelectrolyte chain during the self-assembly were estimated on the basis of available theoretical and experimental data for aqueous polyelectrolyte solutions. The analysis revealed that both ionic and hydrophobic interactions must be taken into account considering LBL multilayer formation. By using new data on adsorption of proteins, dyes, polymers, and nanoparticles it was demonstrated that the proposed approach to LBL explained a number of experimental observations that were difficult to rationalize in the framework of a pure electrostatic mechanism. (C)1999 Acta Metallurgica Inc.